U.S. Pat. No. 3,693,122 entitled "Flux Transfer Trip Device for Electric Circuit Breakers" describes a flux shifter unit that interacts with the circuit breaker operating mechanism to separate the circuit breaker contacts upon occurrence of an overcurrent condition within a protected electrical distribution system. A flux diverter element interfaces between the holding magnet and the powerful driving spring to insure immediate response to a flux cancelling electrical signal.
The flux shifter described within U.S. Pat. No. 4,251,789 is smaller in size and requires a lower energy flux cancelling electrical signal. The smaller associated holding magnet and driving spring are used to release a small-sized target to indicate the occurrence of an overcurrent interruption function.
U.S. Patent application Ser. No. 08/248,910, filed May 25, 1994 entitled "Combined Bell Alarm and Lock-out Accessory" describes a circuit breaker accessory that can be installed within the circuit breaker cover as one of a plurality of selectable circuit breaker accessory functions.
When the accessory is contained within the circuit breaker compartment within an industrial environment, the vibrations associated with certain manufacturing processes are too intense to allow the use of small flux shifter devices as disclosed within the aforementioned U.S. Pat. No. 4,251,789 without causing the flux shifter to release from the holding magnet.
The large electrical signal required to release the flux shifter disclosed within the aforementioned U.S. Pat. No. 3,693,122 is not available when the accessory device is used with and electronic trip unit due to the requirement that the flux shifter be released after the source of energy to the trip unit is interrupted.
One purpose of the invention is to provide a smaller sized flux shifter unit that is releasable by means of a small pulse electrical signal and is immune to the impact and vibratory forces associated within an industrial environment.